Overflow device for vehicular carburetor

ABSTRACT

An overflow device for a vehicular carburetor. The carburetor includes a float chamber in which a maximum level is to be maintained. A drainage tube drains fuel at higher levels to a reservoir at an elevation lower than the carburetor. A vent tube vents the reservoir at an elevation higher than the carburetor. The reservoir can be heated by engine heat to evaporate excess fuel.

FIELD OF THE INVENTION

This invention relates to an overflow device for the carburetor of avehicle such as a motorcycle or tricycle vehicle.

BACKGROUND OF THE INVENTION

A motorcycle or tricycle vehicle equipped with balloon tires isfrequently used to run offroad, i.e., on an undulating field so that thefluid level in the float chamber of the carburetor moves up and down. Inorder to control the fluid level in the float chamber, there has beenadopted means in which the float chamber is formed with an overflow portconnected with a pipe for discharging the fuel which has overflowed.

While running off the road, however, the vehicle may run in a deep pondor pool. In this instance, since the motorcycle or tricycle structurallyhas its engine disposed at a relatively low position, the carburetor isalso disposed at an accordingly low level. Consequently, if theaforementioned overflow pipe is in a depending position, its open endmay dip into the water. This may invite backflow of water into the floatchamber so that water is mixed into the fuel, thereby to cause theengine to be troubled or stopped.

The present invention has been conceived in view of the background thusfar described and contemplates to provide an overflow device for avehicular carburetor, by which the backflow of water is blocked toprevent the engine from being troubled or stopped without adverselyaffecting the overflow function.

BRIEF DESCRIPTION OF THE INVENTION

This invention is carried out in combination with a carburetor which hasan overflow port from its float chamber. A fuel reservoir is mounted tothe vehicle at an elevation below that of the carburetor, and has an airvent which vents to the atmosphere at an elevation above that of thecarburetor.

The invention will be described in connection with one embodimentthereof, with reference to the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation showing one embodiment of the invention;

FIG. 2 is a top plan view of FIG. 1;

FIG. 3 is a sectional view of a carburetor;

FIG. 4 is a side elevation showing a crankcase; and

FIG. 5 is a cross-section taken at line V--V in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

The accompanying drawings show a tricycle vehicle for offroad runs. Abody 1 which is made of a pipe frame. To the front end of frame 1 thereis attached a steering handle 2, to the lower end of which is attached afront or steering wheel 3 equipped with a balloon tire. To the rear endof frame 1 there are attached two rear or drive wheels 4, also equippedwith balloon tires.

An engine, e.g., a two-cycle air-cooled engine 5 is carried on frame 1at a relatively rearward position. Engine 5 is connected with acarburetor 6 and an air cleaner 7. Air cleaner 7 is equipped at theother side of the sheet of FIG. 1 with an air inlet 8 which is openedforwardly relative to the direction of forward motion of the vehicularbody. Above engine 5, carburetor 6 and air cleaner 7, there is disposeda seat 9 which is fixed to a seat rail 10. Carburetor 6 is connectedwith a fuel tank 11 which is disposed at a front position of frame 1.

Carburetor 6, thus connected, is so constructed as is more specificallyshown in FIG. 3. That is, an intake passage 12 has its effective areacontrolled by a piston valve 13. Piston valve 13 is equipped with aneedle valve 14 for opening and closing a needle jet 15. Needle jet 15is made to communicate with a float chamber 16, in which is mounted afloat 17 and in which is mounted an overflow pipe 18 rising to protrudefrom a preset fluid level. Overflow pipe 18 has its upper end formedwith an overflow port 19 which is made to communicate through theaforementioned pipe 18 with a tube (or pipe) 20 shown in FIG. 1.

Below, there is disposed the crankcase 21 of engine 5, which isconstructed as specifically shown in FIGS. 4 and 5. That is to say,crankcase 21 has an opening at one side of its body 22 closed with acase cover 23. Case cover 23 is integrally formed with a fuel reservoir24. Fuel reservoir 24 is constructed of a cover wall 25 of theaforementioned case cover 23, a peripheral wall 26 integrally extendingout of the cover wall 25, and a stop cover 27 closing the open end ofperipheral wall 26. Peripheral wall 26 is formed with a recess 28therein, which is made to communicate with the inside of the crankcase21 so that it is entered by the engine oil 29 which is stored in thecrankcase 21. The stop cover 27 is made of a material such as asynthetic resin and is sealingly attached to the open end of theperipheral wall 26 through a packing 30 and screws 31. Moreover, stopcover 27 is integrally formed with an inlet port 32, which hascommunication with fuel reservoir 24, and an outlet port 33 throughwhich the fuel gasified in the fuel reservoir 24 flows out. With theaforementioned inlet port 32, there is connected the aforementionedoverflow tube 20 which in turn is connected with the overflow pipe 18.On the other hand, another discharge tube 34 is connected with theaforementioned outlet port 33. Discharge tube 34 is formed at itsleading end with an air vent 35 (FIG. 1), which is inserted into theopening 38 of a main pipe 37 disposed above the carburetor 6. A fixture39 is provided for fixing discharge tube 34 to seat rail 10.

To case cover 23 of crankcase 21 there is fastened, as shown in FIG. 4,a clutch cover 40 which is formed with an engine oil inlet 41 closed bya cap 42. As a result, engine oil 29 in crankcase 21 can be suppliedthrough oil inlet 41.

In the case of an offroad run, i.e., a run on an undulating road orfield, the tricycle vehicle thus constructed is intensely vibrated, andthe fuel level in float chamber 16 of the carburetor 6 accordingly movesup and down. If the fuel level becomes higher than the overflow port 19,excess fuel flows out of overflow port 19 into overflow tube 20 throughoverflow pipe 18. As a result, it is possible to control the fuel levelin that float chamber 16 without blocking overflow in the float chamber16.

On the other hand, the fuel thus stored in the fuel reservoir 24 partlyevaporates in a spontaneous manner and is partly forced to evaporate bythe heat of the crankcase. More specifically, the engine oil 29 incrankcase 21 is stored at a high temperature because it has alreadypartly lubricated and partly cooled the respective parts of the engine.The heat of engine oil 29 is conducted through cover wall 25 andperipheral wall 26 of case cover 23 to the fuel reservoir 24 so thatfuel in fuel reservoir 24 is evaporated. Thus, the fuel havingoverflowed into fuel reservoir 24 is instantly gasified so that thecapacity of the fuel reservoir 24 can be minimized.

The fuel thus gasified is guided by discharge tube 34 until it isdischarged to the atmosphere from air vent 35 through opening 38 of mainpipe 37.

With the construction thus far described, therefore, even if the vehicleruns in a deep pond or pool, no entry of water takes place through airvent 35 of discharge tube 34 because air vent 35 is opened at arelatively high elevation on frame 1. As a result, there is no fear ofany water entering into float chamber 16 of carburetor 6, and the engine5 will not be stopped or troubled by entry of water. Moreover, sincedischarge tube 34, extending upward, is inserted into main pipe 37, itis free from entry of rain droplets.

As is apparent from the foregoing description, the present inventionshould not have its application limited to the tricycle but can also bepracticed in a motorcycle.

Moreover, fuel reservoir 24 should not necessarily be limited to theconstruction shown, in which it is mounted in the crankcase 21. It issufficient merely that reservoir 24 be positioned at an elevation belowthat of carburetor 6.

According to the present invention, the overflow port formed in thecarburetor is made to communicate with the fuel reservoir which isdisposed below the carburetor, and the fuel reservoir itself isconnected with an air vent which is disposed above the aforementionedcarburetor. According to this construction arrangement, therefore, thefuel having overflowed from the carburetor flows down into the fuelreservoir and then evaporates to the atmosphere through the air vent,thereby to ensure the overflow so that the fuel level in the carburetorcan be very accurately controlled. Since, moreover, the air vent ispositioned above the carburetor, even if any parts of the vehicular bodydip into the water in the case of runs in a pond or pool, that air ventis never submerged in the water so that no water can flow back into thecarburetor. Consequently, there is no fear of any water being mixed intothe fuel to stop or to perturb the engine.

This invention is not to be limited by the embodiment shown in thedrawings and described in the description, which is given by way ofexample and not of limitation, but only in accordance with the scope ofthe appended claims.

We claim:
 1. An overflow device for a vehicular carburetor which iscarried on the body of a vehicle and includes a float chamber whoseoverfilling is prevented by drainage through said overflow device, saidoverflow device comprising: a reservoir disposed at an elevation beneathsaid float chamber, an overflow tube opening into said float chamber atan intended maximum fuel level therein and discharging into saidreservoir, and a vent tube rising from an upper level in said reservoirto a vent opening at an elevation above said carburetor.
 2. Apparatusaccording to claim 1 in which said reservoir is disposed in a locationto be heated by engine heat for the purpose of evaporating fuel therein.3. Apparatus according to claim 2 in which said reservoir is integralwith the crankcase of said engine, and heated by engine oil. 4.Apparatus according to claim 1 in which said vent opening is disposed ina shrouded portion of said body to resist entrance of water therein. 5.Apparatus according to claim 2 in which said vent opening is disposed ina shrouded portion of said body to resist entrance of water therein. 6.Apparatus according to claim 5 in which said reservoir is integral withthe crankcase of said engine, and heated by engine oil.